Short circuiter for electric motors



Jan. 5 1926.

E. P. LARSH SHORT GIRCUITER FOR ELECTRIC MOTORS Filed Oct. 20, 1923Patented il an. 5, 1926.

EVERETT 1. LABSH, OF DAYTON, OHIO.

SHORT CIRCUITER FOR ELE CTRIC MOTORS. I

Application filed October 20,'1923. Serial No. 669,716.

To all whom it may concern:

Be it known that I, EVERETT P. LARsH, a citizen of the United States,residing at Dayton, in the county of Montgomery and State of Ohio, haveinvented certain new and useful Improvements in Short C-ircuiters forElectric Motors, of which the following is a specification.

This invention relates to electric motors and more particularly to ashort circuiting or operation changing device'for automaticallyconverting an alternating current motor from a repulsion startingcondition to an induction running condition and vice versa in accordancewith the variations of speed.

The. present construction embodies in a single structure the,advantageous features of both theflgovernor weight and garter springtype of short circuiting devices. One of the purposes of theconstruction is to give definition to the movement of the shortcircuiting members by which their movements' into and out of contactwith the commutator bars will be decisive and which will eliminate thedisadvantages of a gradual engagement and disengagement. Theconstruction is further designed to embody the advantages of both thebutt contact and the wiping contact.

To this end, the construction embodies an annular series ofcentrifugally controlled contact members located adjacent to the lateralor terminal face of the commutator and under centrifugal influence,possess a limited degree of oscillatory movement into butt contact withthe ends of the commutator bars and upon further acceleration of speedpossess expanding or radial movement in which they wipe the contactedends of the commutator bars to insure clean, b'ri ht, electricalconducting contact surfaces. The

. contact members are inclined or beveled -at their inner ends wherebythey normally extend in inclined relation with the axis of rotation inwhich position they are yieldingly that their center of gravity isnormally displaced laterally beyond the plane of the annular resistancespring and in offset relation with the pivotal point or fulcrum of suchmembers in their oscillatory movement. The

'centrifugal action upon rotation of the short circuiting device tendsto move the center of gravity of the contact members mto the plane ofrotation of its fulcrum or u-nter of oscillation which, in the presentcase, is at the opposite side of the plane of the restraining band orannular spring. The

Y movement of the contact members being limtion in a radial directionagainst the tensionor retractive action of the garter spring. The shortcircuiting'parts are enclosed and protected within a housing formed by adisc having an inclined inargiha'l1 flange approaching the ends of thecommutator bars between which flange and the ends of the bars theextended members are wedged at the limit of their outward movement.

The object of the invention is to simplify the structure as well as themeans and mode of operation of such circuit changin devices whereby theywill not only be c capened in construction, but will be more efficientin use, automatic in operation, uniform in action, automaticallycontrolled and unlikely to getout of repair.

A further object of the invention is to provide such centrifugallycontrolled short circuiting means which will promptly respond tovariations of speed above and below a predetermined rate of rotation.

A further object of the invention is to i provide a short circuiting orcurrent changing device which will have a definite make and breakcontact combined with a wiping action insuring perfect electricalcontact and in which any clatter or vibration and the in cident arcingand burning of the contact surfaces will beelim'inated.

A further object of the invention is to provide such a short circuitingor current changing device which will be of compact form containing fewparts and no pivotal joints or indirect movements, but in which thecurrent controlling devices are directly operated by centrifugaltendency. 7

With the above primary and other incidental objeots in view as will morefully appear in the specification, the invention consists of thefeatures of construction, the

parts and combinations thereof, and the mode of operation, or theirequivalents as hereinafter described and set forth in the claims.

In the accompanying drawings wherein is shown the preferred butobviously not necessarily the only form of the embodiment of theinvention, Fig. 1 is a longitudinal sectional view of a motor commutatorto which the present form of short circuiting device has been applied.Fig. 2 is an end elevation of the commutator and short circuitingdevice, portions of which have been broken away. Fig. 3 is an enlargeddetail View in which the relative movement of the short circuit deviceis diagrammatically indicated. Figs. i and 5 are similar views of amodification.

Like parts are indicated by similar characters of reference throughoutthe several views.

. The structure of the electric motor per se, forms no part of thepresent invention, which pertains wholly to the short circuitlng meansfor the commutator bars, by which the motor is caused to operatealternately as a repulsion motor and an induction motor.

An alternating current, repulsion-induction motor of the single phasetype to which the present invention is particularly adapted isone whichas the name indicates, starts as a repulsion motor and as the speedapproacheslts normal or maximum rate of rotation automatically changesits character,

and runs as an induction motor. Briefly described, it consists of afieldor stator of laminated toothed construction having a single windingthereon connected to the supply'clrcuit and a progressively woundarmature or rotor with acommutator engaged by brushes during thestarting or repulsion period together with speed controlled devices forshort circuiting the armature windings through the commutator after thearmature has attained a predetermined speed, which speed controlledmeans in some instances lifts the brushes from the commutatorsimultaneously with the short circuiting operation. There is noelectrical connection between the stator and the rotor.

. The currents in the stator create an alterthe rotor or armatureapproaches a synchronous speed or one commensurate with the windings,whereupon the speed controlled devices operate to automatically shortcircuit the armature winding through the commutator. Thus the motor isautomatically transformed from a repulsion type into an induction motorhaving what is essentially a squirrel cage rotor. ment of the speedoperated governing or short circuiting device which forms the subjectmatter of the present invention. One of the the advantages of a'machineof this type is that it is inherently a constant speed motor having ahigh starting torque with low current consumption or minimum currentsurge.

The typical repulsion motor without compensation gives the mostefficient starting torque possible while the single phase inductionrotor with the squirrel cage armature or its equivalent affords the mostefficient motor when running.

A repulsion-induction type of motor combines these most desirablequalities in a single machine. As it possesses such high starting torquecharacteristics it is well adapted for operating machinery which startsunder full load, as pumps, air compressors, grinding mills, etc.Requiring no starter, they are adapted for automatic control .ordistance operation. They start quickly and operate quietly and smoothly.

The above is offered merely to facilitate a thorough understanding ofthe purpose of the invention, and with no intent nor de sire that itshall in any way be construed as limiting or restricting the applicationor scope of the invention.

Inasmuch as the construction of the motor per se forms no part of thisinvention, it has not been illustrated. It is to be understood, however,that the short circuiting moans forming the subject matter hereof isapplicable to various styles of motors of the character heretoforeindicated. Referring to the drawings, 1 is the armature shaft, on whichis carried the usual commutator comprising the core 2 about theperiphery of which are located a continuous succession of commutatorbars 3, insulated from the core 2 and from each other by interveningbodies of insulating material.

In the present instance, the commutator bars 3 are shown terminatingflush with the core 2 and in a plane perpendicular to the axis ofrotation. however, that if desired the commutator bars 3 may projectbeyond or overhang the face of the core 2 and that further they may, ifdesired, be inclined or beveled at their ends and the contact membershereinafter described similarly beveled or inclined for co-operativeengagement therewith.

The short circuiting means is embodied in a unitary structure capable ofbeing assembled independent of the motor and applied thereto or removedtherefrom without the necessity of disassembling either the motor or theshort circuiting unit. However, the short circuiting device may, ifdesired, be assembled directly upon the motor shaft.

It is to be understood It is the improveof the invention as illustratedin the draw- I ,ings, there is employed a disc 6 adapted to v be securedto the armature shaft 1 adjacent to the face of thecommutator but inspaced relation therewith. This disc 1 forms a mounting and housing forthe short circuit.

ing members. The disc 6 is formed with an inclined marginal flange 7projecting toward the commutator in converging spaced relationtherewith. -The disc 6 is further provided with an inner flange 8forming a sleeve or hub which fits the armature shaft 1. The disc orhousing 6 is secured to the shaft 1 by the clamp ring 9 threaded uponthe shaft.

Located within the. housing 6 is an annular series of independentcontact members 10. These contact members are slightly sector or wedgedshape and are assembled side by side in an annular series in which eachcontact member is radially disposed in relation with the axis of theshaft. The

' contact members 10 are each formed with a lateral notch 11 whichregisters with like notches in the adjacent contact members to form anannular channel or pocket in the outer face of the assembly of contactmembers. The formation of this pocket or channel by provision of thenotches 11 affords upon each contact member a laterally projecting-armor finger 12 at the inner ends of the contact members. annular recess orpocket afforded by the registering notches 11 is an elastic retractingband 13. 'In the present instance, the retracting band 13 comprises anendless helical spring generally known as a garter spring. Theretractive tendency of this annular band or spring 13 seats the innerends of the contact member 10 upon the inner sleeve or hub 8 of thehousing 6. The inner ends of the contact members or short circuitingelements are slightly inclined in relation with the contact faces ofsuch members whereby, when in retracted relation with the terminal edgesof the contact members seated upon the inner sleeve or hub 8, thecontact faces 14 are spaced away from the ends of the commutator bar 3.Sufficient clearance is provided however that, upon oscillationof themembers 10, the faces '14 may be brought into engagement with the endsof the commutator bars 3. To

' efiect such contact, the members 14) fulcrum upon their inner, corners15 while the outer ends of the members swing toward the commutator barsunder centrifugal influence as hereafter described.

The contact members or short circuitlng elements 10 are so proportionedand shaped that when in their normal retracted or seated position underthe influence of the retractive band 13, the preponderance of weight ofsuch members or the center of gravity Seated within the face of thecommutator and offset in relation with the plane of rotation of thefulcrum point 15 and, in fact, beyond the plane of rotation of theretractive spring member 13. The annular s ring or elastic band 13- byits contraction a out the fingers or arms 12 tends to turn thecontactmembers 10 outwardly about their fulcrum points 15 into their retractedor inoperative positions wherein, as before stated, the center ofgravity of the contact member is offset in relation with theplane ofretraction of the spring.

As the commutator is. rotated, the short circuiting elements are carriedwith it. The centrifugal influence induced by rotation of the commutatortends to move the center of gravity of the contact members into theplane of rotation of their points of restraint. That is, the points ofengagement of the garter spring or' elastic band 13. During thismovement the contact members or short circuiting elements will fulcrumupon their inner points 15 thus tilting the .arms or. fingers 12outwardly and subjecting the elastic band or garter spring 13 toextension. This oscillatory movement of the contact members 10 causesthe faces 14 thereof to contact with the adjacent ends of the com-'mutator bars 3 and such movement is effected against the tension of theelastic band or spring 13. This initial position of contact is shown bydotted lines in Fig. 3. Upon further'increase of speed the centrifugalinfluence upon the members 10 will cause them to move outwardly withsliding or wipin contact upon the ends of the commutator ars against thetension of the re-. tractive band or garter spring 13 to their finalposition shown by dash lines in Fig. 3.

.In such final position, the outer ends of the contact members 10 engageand ride upon the inclined peripheral flange 7 of the disc or housing 6.Thisflange exerts a camming action which in conjunction with thecentrifugal influence tends to press the contact members more firmlyinto the contact with the ends of the engaged commutator bars 3.

It will require an appreciable amount of influence or force to overcomethe inertia of the contact members 10 as well as to over come theretractive tendency of the elastic band or garter spring 13. However,when the speed is reached at which such oscillation. of the contactmembers takes place, less effort will be required to move the contact'-members astheir centers of gravity approach the face of the commutator.Consequently such oscillatory movement, once initiated, will cause themembers to quickly contact the ends of the bar. That is to say, itrequires more effort to start the contact members from their positionsof rest than to continue their movement into engagement with thecommutator bars and the resistance to such movement progressivelydecreases, thereby insuring a quick and decisive shiftng movement underthe initial impulse: In like manner, the retractive movement of thecontact member is a quick and decisive shifting movement under theinitial impulse. In like manner, the retractivc movement of the contactmember is a quick and decisive one. as the centrifugal influence isrelaxed to a point'of equality with or slightly below the equalinfluence of the spring or elastic band 13, the latter overcomes thecentrifugal influence of the weight of the contact members tending tooscillate them outwardly about their fulcrum 15, the retractiveinfluence of the spring being progressively increased as the leverage ofthe fingers or arms 12 increases thereby accelerating the breaking orreleasing movement of the short circuiting members 10. Before thisreleasing or breaking movement is effected, however, the contact membersare slidingly shifted in radial directions inwardly from their extremeoutward operative positions to'their inner positions in which thefulcrum points 15 engage the flange or hub 8 of the housing 6 ,uponwhich points 15, the members then fulcrum under the retractive influenceof the band or spring 18. The construction thus affords a sliding orwiping engagement in both directions and insures quick make and breakmovement by which arcing and burning of the contact faces is minimized.

In Fig. 5 there is shown-a modification, wherein in lieu of the annularretractive spring 13, ayielding collar 16 engages the arms 12, andconstitutes the tension member hereafter mentioned in the claims againstthe yielding resistance of which the contacts are movable undercentrifugal influence. The collar has a beveled ace 17 which by itscammin action, as th collar is urged axial- 1y by tile helicalcompression spring 18, exerts a retractive influence upon the contactslu s. The camming pressure of the beveled 001%11 retracts the contactsinward when distended, and also tends to oscillate them outward and awayfrom the commutator when in their innermost positions. The overhangingmarginal flange 19 limits the outward movement of the contacts. Therelative location of the centers of gravity of the contacts and theiraction under centrifugal influence is substantially the same asbeapparent that there is thus provided a device of the characterdescribed possessing the particular features of advantage beforeenumerated as desirable, but which obviously is susceptible ofmodification in its form, proportions, detail construction andarrangement of parts without departing from the principle involved orsacrificing any of its advantages.

While in order to comply with the statute the invention has beendescribed in language more or less specific as to structural features,it is to be understood that the invention is not limited to the specificdetails shown, but that the means and construction herein disclosedcomprises the preferred form of several modes of putting the inventioninto effect and the invention, is, therefore, claimed in any of itsforms or modificatio'ns within the legitimate and valid scope of theappended claims.

Having thus described my invention I claim:

.1. In a short circuiting device for motors, an annular series ofradially disposed centrifugally actuated weights arrangedcircumferentially of the motor shaft, a bearing point adjacent the innerend ofeach weight about which the weight is capable of lateraloscillatory movement to and from the motor commutator, and an annularcontractile band circumferentially engaging portions of said Weightsagainst the yielding resistance of which the weights are movable abouttheir bearing points under centrifugal influence to effect the shortcircuiting of the motor commutator.

2. In a short circuiting device for motors, an annular series ofradially disposed centrifugally actuated weights arrangedcircumferentially of the motor shaft, a laterally extending arm on eachweight normally extending in approximate parallelism with the axis ofrotation of the motor shaft and an annular tension member common to allthe weights and circumferentially engaging the lateral arms thereof toyieldingly resist the movement of the weights under centrifugalinfluence, and against the tension of which the weights effect theinterconnection of the motor windings.

3. In a short circuiting device for motors, an annular series ofradially disposed centrifugally actuated weights arrangedcircumferentially of themotor shaft, each weight member being laterallyindented and a helical spring the ends of which are inter-. connected toform an annular contractile band-common to the weights engaging in thelateral indentures thereof, against the yielding resistance of which theweights are moved by centrifugal influence to effect the interconnectionof the motor windings.

4. In a short circuiting device for motor 'commutators, an annularseries of weights arranged circumferentially of the motor to all theweights and exteriorly surrounding portions thereof, against theyielding resist ance'of which the weights effect their tilting movementunder centrifugal influence.

5. In a short circuiting device for commutators, an annular series ofweights arranged circumferentially of the motor shaft and revolubletherewith, said weights being capable of tilting movement toward andfrom the commutator under centrifugal influence to effect shortcircuiting of the motor commutator, a contractile band common to all theweights of the series and an annular seat for the contractile bandformed in said weights in which the band is engaged to 'yi'eldinglyrestrain the tilting movement of the weights.

6. In a short circuiting device for motors, a plurality of centrifugallycontrolled elements arran ed circumferentially and operable in radialplanes relative to the-armature shaft, said elements being laterallynotched and an annular contractile band engaged in the registeredlateral notches of the elements and acting to restrain the centrifugalaction thereof as .said elements are rought in contact with thecommutator" of the motor.

'7, In a short circuiting device for motors the combination with acommutator, of a short circuiting element consisting of a series ofsegmental weights arranged circum ferentially of the motor shaft andcapable of both lateral tilting and radial movement under centrifugalinfluence and an annular tension member in engagement with the weights,and acting to'restrain the tilting and radial movement thereof.

8. In a short circuiting device for motors, a plurality of contactmembers arranged side by side in an annular series circumferential- 1yof the motor shaft and normally inclined away from the motor commutatorand an annular tension member against the resistance of which saidcontact members are initially oscillated toward the commutator andsubsequently moved radially under centrifugal influence.

9, In a short circuiting device for motors, a plurality ofcentrifugallyoontrolled weights arranged side by sidelin an annularseries circumferentially of the motor shaft, and an annular tensionmember restraining said weights against movement, said weights beingnormally positioned with their centers 0f gravity offset laterallybeyond the plane of restraining influence of the tension member, wherebycentrifugal action will tend to oscillate said weights to move theircenters of gravity into the plane of restraining influence, suchmovement of the weight members serving to effect the short circuiting ofthe motor windings.

10. In a short circuiting device for electric motors, the combinationwith a commutator of an annular series of short cirof the motor shaftand centrifugally actuated into engagement with the commutator bars,said elements having therein laterally opening registering notches, andan annular elastic band seated in the registering lateral notches andacting to restrain the centrifugal action thereof.

11. In a short circuiting device for motors, an annular series ofradlally disposed centrifugally actuated weights arrangedcircumferentially of the motor shaft, a concentric seat at the innerends of the weights upon which the weights fulcrum foroscillatorymovement under centrifugal influence and an annular tension membercircumferentially enclosing portions of 'said weights and exertingcontractive influence upon said weights in a plane offset in relationwith their fulcrum points, against the yielding resistance of which theweights are oscillated by centrifugal influence to effect theinterconnection of the motor windings.

12. In a short circuiting device for motors, an annular series ofradially disposed centrifugally actuated weights arrangedcircumferentially of the motor shaft a fulcrum bearing for each weight,about which the weight 1s capable of oscillatory movement into and outof short circuiting position, and an annular tension member common tothe weights en aging the weights at points outwardly ra ially disposedrelative to their fulcrum points and out of the plane thereof againstthe yielding resistance of which the'weights are capable of oscillatorymovement to effect the interconnection of the motor windings.

13. In a short circuiting device for motors, an annular series ofradlally disposed centrifugally actuated weights arrangedcircumferentially of the motor shaft, a restraining member common to theweights comprising a helical spring having its ends interconnected toform an annular contractile band, operatively engagin with said weights,the centers of avity o the weights being located radially yond andlaterally out of the plane of the restraining member against theyielding resistanceof which the weights are movable under centrifugaltendency to effect the interconnection of the motor windings. v

14. In a short circuiting device for motors, an annular series of radally disposed centrifugally actuated weights arranged circumferentiallyof the motor shaft,.a tenable.

sioned restraining member comprising an annular contractile bandoperatively engaged with the weights, a fulcrum for each weight at theinner end-thereof, the centers of gravity of the weights being normallylocated radially beyond and laterally out of the plane of the fulcrumsabout which the weights are movable against the tension of theestraining member under centrifugal influe. cc to effect theinterconnection of the motor windings.

15. In a short circuiting device for motors,

an annular series of radially disposed centrifugally actuated weightsarranged circumferentially of the motor shaft, said weights beingcapable of both oscillatory and radial movement under centrifugalinfluence, to efl'ectthe interconnection of the motor windings and ayieldable restraining member common to the weights yieldingly resistingboth the oscillatory and radial movement of the weights.

16. In a short circuiting device for electric motor commutators, anannular series of weights arranged circumferentially of the motor shaftand revoluble therewith, said weights being radially movable undercentrifugal influence, said weights having in their radially disposedmarginal edges a series of registering notches, and a contractile bandengaging within the registering notches and yieldingly resisting theradial movement of said weights under centrifugal influence to effectthe short circuiting of the motor commutator.

17. In ashort circuiting device for motor commutators, an annular seriesof weights arranged circumferentially of the motor shaft and revolubletherewith, said weights being movable under centrifugal influence toeffect the short circuiting of the motor commutator, arms upon theweights extending axially relative to the motor shaft, and a contractileband surrounding the arms of the series of weights against the yieldingresistance of which the weights are mov- 18. In a short circuitingdevice for motor commutators, an annular series of weights arrangedcircumferentially of the motor shaft and revoluble therewith, saidweights being movable under centrifugal influence to effect the shortcircuiting of the motor commutator, said weights being laterallyrecessed, and a contractile band seating in the lateral recesses of theseries of weights against the tension of which the weights are movableunder centrifugal influence.

19. In a short circuiting device for motor commutators, an annularseries of weights arranged circumferentially of the motor shaft andrevoluble therewith, said weights being movable under centrifugalinfluence to effect the short circuiting of the motor commutator, acontractile band common to the weights of the series and an annular seatfor the contractile band, formed in the lateral margins of said weights,in which the band is laterally engageable to restrain the movement ofsaid weights.

20. In a short circuiting device for motor commutators of thecharacterdescribed, an annular series of weights circumferentiallyarranged relative to the motor shaft, said weights being radiallymovable under centrifugal influence to effect the short circuiting ofthe commutator, .a series of registering indentations in the lateralmargins of said weights and a contractile band common to the weightsseated in said registering indentations ag inst the tension of which theweights are-jlradially movable.

21. In ashort circuiting device for motor commutators of the characterdescribed, an

annular series of weights circumferentially arranged relative to the,motor shaft, said weights being movable under centrifugal influence toeffect the short circuitin of the commutator, a series of registeringindentations in the lateral margins of said weights and a contractileband common to the weights seated in said registering indentationsagainst the tension of which the weights are movable' In testimonywhereof, I have hereunto set my hand this 4th day of October, A. D.

. EVERETT P. LARSH.

